Process for the manufacture of paper pulp



Patented Aug. 4, 193K untrue snares enrich;

ERIC 'WAHLFORSS, OE ST. CLOUD, MINNESOTA, ASSIGNOR, BY MESNE ASSIGNMENTS,

IQ ARTHUR D; LITTLE INDUSTRIAL CORPORATION, OF NEW YORK, N. Y., A G03- JPORATIQN 0.? DELAWARE PRDCESS FOR THE MANUFACTURE OF PETER PULP Ito Drawing.

The present invention relates to a new and improved process for the production of paper pulp from hard woods, together with the product resulting from such a process.

According to existing practice, pulp for paper-making purposes is ordinarily prepared either mechanically or chemically. In the mechanical method the wood ordinarily soft or coniferous is reduced to a finely divided form suitable for the paper-making operation by grinding- Although this method has certain advantages from the standpoint of cost and is quite commonly employed in large scale-production for the manufacture of newsprint and similar forms of paper, nevertheless it does result in a perceptible shortening'of the cellulose fibres with a resultant impairment in strength of the finished paper. In the chemical method the or ganic encrusting substances other than the cellulose fibres are substantially completely removed from the natural Wood through the use of. chemical reagents. The cellulose fibres thus freed from surrounding encrustations are then adapted for the subsequentpapermaking operations. It is impossible to con-.

trol the chemical method of digesting the natural wood with suflicient accuracy to insure the removal of all of the organic encrusting substances without also digesting a certain percentage of the cellulose fibre. In consequence, the resulting pulp not only loses a certain percentage of cellulose fibre initially present but is weakened, due to impairment in strength of the remaining fibre as a result of the digesting. According to the Kraft process so-called, the cooking or digesting of the natural wood with chemical reagents is halted before the ligneous and intercellular materials have been completely removed and insuring that all of the cellulose fibre origi nally present in the wood is retained. The pulp obtained by virtue of this process is darkened somewhat by the presence of a residuum of organic material, but contains all of the cellulose fibre'in substantially its initial volume and strength.

lln addition to these methods commonly employed for the production of paper pulp, it has been suggested that both the chemical Application filed July 30, 1926. Serial No. 126,081

and mechanical methods of preparing the pulp be preceded by treatment with steam or hot water to soften the wood and facilitate the subsequent grinding or chemical operations. These suggestions are also intended to permit the use of certain resinous woods not otherwise capable of satisfactory employment for the production of pulp for papermaking purposes. Where this result is intended, the precooking with steam is designed to remove the resins and similar mate rials from coniferous woods in order to enablethis type of wood to be successfully reduced to a pulp by the usual chemical operation.

I have discovered that it is possible to produce a grade of pulp from hard wood well suited for-certain types of paper products Without resorting to mechanical grinding of the raw material or the use of added chemical reagents. This pulp may be introduced directly into the usual paper-making process without further treatment, and as an example may be employed either alone or in admixture with kraft pulp in the field in which kraft is now commonly used. I accomplish the desired result by converting the organic, encrusting substances surrounding the fibre of the hard wood into a condition sufficiently plastic-to permit displacement andseparation of the fibres without grinding or further chemical treatment. The product resulting from this conversion of the organic encrustmill or rod mill for the purpose of further displacing and separating the fibre bundle. have foundthat the desired result can be satisfactorily attained by treating the raw material under pressure with certain volatile substances and organic compounds extracted directly from the material itself. To this end the wood is initially subjected to the action of water or water vapor at a substantialtem- ,perature and pressure, the operation being sively extracted from the wood. In actual practice I have found that the operation may be satisfactorily carried out in a closed cham her at pressures of to 100 pounds for a period approximating two hours, and at a temperature corresponding to the temperature of steam at the given pressure. Althou h this relatively hig pressure is desirab e, nevertheless. experiments have indicated that lower pressures with a longer period of treat: ment may sufiice to accomplish the desired result, and accordingly my invention contemplates the treatment of the raw material under pressures and temperatures and for a sufficient period of time to obtain the desired plastic condition of the organic, encrusting substances without charring the wood or substantially breaking down the cellulose fibres. At the completion of this operation the resulting fibrous material may be subjected to an impact operation of the character performed in a ball or rod mill, and thereafterconverted into paper in the usual manner.

Under certain circumstances it maybe desirable to utilize the liquor resulting from the treatment of the raw material in subsequent operations, and with this in mind I propose to save the li uor after the removal of the pulpy mass an 'use this liquor with the addition of whatever water may be necessary for the treatment of the next succeeding batch of wood. It is my belief that up to a certain point the increasing strength of the li uor resulting from the extraction of cor tam volatile and organic substances from the wood will facilitate subsequent operations. However, although the reuse of this liquor is desirable, it is nevertheless not essential to the proper functioning of my process..

In the actual practice of my process I have immersed hard wood in the form of chips in a closed vessel or chamber in the presence of water without the addition of chemical reagents. The temperature of the water and wood is then elevated through the application of external heat until a pressure of 100 pounds is obtained within the chamber, This pressure is maintained through proper control of the heat for a period approximatin two hours without permitting the escape of any substantial quantity of vapor from with in the chamber.- At the completion of the operation, the hard, brittle, encrusting substances have'been reduced to a soft and relatively plastic mass which permits further separation and displacement of the fibre bundle by a simple impact operation.

I consider that without grinding or digesting with added chemical reagents I have been ableto produce a new substance adaptable for use directly in the paper-making from hardwood in chip or similar operation in the same fashion as existing forms of aper pulp.

The su stances present in the natural wood may be generally classified as organic materials, and I believe that in the practice of my process the cookin of the wood in the presence of water gra ually develops or releases the volatile, organic materials which in turn react upon and soften the normally hard encrusting substances. Although a certain percentage of these encrusting substances may be removed from the resulting pulp, nevertheless 'I have demonstrated by actual experiment that the major portion of these encrusting substances remain in the pulp. a

What is claimed is:

1. The process of producingpaper pulp form which consists in convertmg the orgamc encrustlng substances initially present in the hardwood into a condition sufficiently plastic to permit spreading and separation of the individual fibres without material disintegration of the fibres and while still surrounded by the major portion of the encrustin substances, and thereafter removing an subjecting the softened fibrous mass to an impact or like operation to further complete the preparation of pulp for paper making purposes.

2. The process of producing paper pulp from hardwood in chi orsimilar orm which consists in subjectrng the wood to the action of organic compounds derived from the hardwood itself when heated in the presence of water to a temperature corresponding to a steam pressure in approximately the range of from 75 to 100 pounds unt1l the organic encrusting substances contained in the hardwood are softened and rendered plastic and the fibrous mass capable of further separationand conversion into pulp without chemical treatment or mechanical pulp ding.

3. iii? process of producing paper plulp from hardwood in chip or similar form w ich consists in subjecting the hardwood under heat and pressure to the action of organic com ounds derived from the wood itself in heatmg the wood in the presence of water to temperatures corresponding to steam pressures, ranging approximately from 75 to 100 pounds, to soften and render plastic the organic encrusting'substances contained in the hardwood without change or material disintegration of the fibres themselves, re-

moving the fibrous mass from the resulting liquor, and reusing the liquor for the next succeeding batch.

4. A material prepared from hardwood and suitable for the production of pulp for paper products, consisting of hardwood fibres having the length in which the fibres naturally occur substantially unshortened bv chemical or mechanical action and surrounded by the major portion of the organic encrusting substances originally present in the wood but softened and rendered plastic throughout in a manner to permit complete separation of the individual fibres without grinding or similarly treating the material, the materialhavin substantially the physical shape and con guration of chip or like form in which cut from the natural wood and a characteristic dark-brown color resulting from the interaction of constituents present in the wood'but being entirely free of chemicals or compounds resulting from chemical constituents other than those originally present in the wood.

5. The process of producing pulp suitable for paper makers purposes from hardwood in chip or similar form which consists in immersing the wood in water in a substantially closed chamber, supplying heat to create a pressure within the chamber in the approximate range of from to pounds, continuing the application of heat for a suflicient period to soften the organic encrusting materials and leave the fibrous structure substantially intact, and thereafter converting the fibrous mass to pulp for paper makers purposes by an impact or similar non-grinding action.

ERIC WAHLFORSS. 

